Color-changing particulate compositions for additive manufacturing and methods associated therewith

ABSTRACT

Additive manufacturing processes, such as powder bed fusion of thermoplastic particulates, may be employed to form printed objects in a range of shapes. Formation of printed objects having various colors may sometimes be desirable. Thermoplastic particulates incorporating a color-changing material capable of forming different colors under specified activation conditions may impart different colors to a printed object. Such particulate compositions may comprise a plurality of thermoplastic particulates comprising a thermoplastic polymer and a color-changing material associated with the thermoplastic particulates, wherein the color-changing material is photochromic and thermochromic. Conjugated diynes, such as 10,12-pentacosadiynoic acid or a derivative thereof, may be particularly suitable color-changing materials having photochromic and thermochromic properties for forming a range of colors upon a printed object. Nanoparticles, particularly silica nanoparticles, associated with an outer surface of the thermoplastic particulates may enhance the brightness of the color obtained under various activation conditions and afford coloration permanence.

FIELD

The present disclosure generally relates to additive manufacturing, andmore particularly, additive manufacturing processes employing powderparticulates that are color changeable during or after forming a printedobject.

BACKGROUND

Additive manufacturing, also known as three-dimensional (3-D) printing,is a rapidly growing technology area. Although additive manufacturinghas traditionally been used for rapid prototyping activities, thistechnique is being increasingly employed for producing commercial andindustrial parts (printed objects) in any number of complex shapes.Additive manufacturing processes operate by layer-by-layer deposition ofeither 1) a stream of molten printing material or a liquid precursor toa printing material or 2) powder particulates of a printing material.The layer-by-layer deposition usually takes place under control of acomputer to deposit and consolidate the printing material in preciselocations based upon a digital three-dimensional “blueprint” (acomputer-aided design model) of the part being manufactured. In aparticular example, consolidation of powder particulates may take placein a powder bed deposited layer-by-layer using a three-dimensionalprinting system that employs a laser or electron beam to heat preciselocations of the powder bed, thereby consolidating specified powderparticulates to form a part having a desired shape. Fusion of powderparticulates in a powder bed may take place by selective laser sintering(SLS), which employs a laser to promote consolidation of powderparticulates via localized heating.

Among the powder particulates usable in three-dimensional printing arethose comprising thermoplastic polymers. Although a wide array ofthermoplastic polymers are known, there are relatively few havingproperties compatible for use in current three-dimensional printingtechniques, particularly when performing particulate consolidation byselective laser sintering. Thermoplastic polymers suitable forconsolidation by selective laser sintering include those having asignificant difference between the onset of melting and the onset ofcrystallization, which may promote good structural and mechanicalintegrity.

As additive manufacturing has become more widely employed for producingprinted objects of various types, access to printed objects having arange of colors has become desirable in many instances. While a colorantsometimes may be successfully incorporated within powder particulatescompatible for use in additive manufacturing processes, this approachnecessitates stockpiling multiple types of powder particulates suitablefor producing a desired range of colors. In addition to higher costs andinventory management issues, this approach may require loading athree-dimensional printing system with different types of powderparticulates at specified times to produce printed objects of aparticular color. For printed objects having multiple colors, the issueof supplying colored powder particulates to the three-dimensionalprinting system may be even more complicated.

SUMMARY

The present disclosure provides particulate compositions suitable foradditive manufacturing. The particulate compositions comprise: aplurality of thermoplastic particulates comprising a thermoplasticpolymer, and a color-changing material associated with the thermoplasticparticulates, the color-changing material being both photochromic andthermochromic.

The present disclosure also provides printed objects formed using theparticulate compositions. The printed objects comprise: a polymer matrixcomprising a thermoplastic polymer, and a color-changing materialassociated with the polymer matrix, the color-changing material beingboth photochromic and thermochromic.

The present disclosure also provides methods for forming printed objectsby additive manufacturing. The methods comprise: providing a particulatecomposition comprising a plurality of thermoplastic particulatescomprising a thermoplastic polymer, and a color-changing materialassociated with the thermoplastic particulates, the color-changingmaterial being both photochromic and thermochromic; and forming aprinted object having a polymer matrix comprising the thermoplasticpolymer and the color-changing material associated with the polymermatrix.

BRIEF DESCRIPTION OF THE DRAWINGS

The following figures are included to illustrate certain aspects of thepresent disclosure, and should not be viewed as exclusive embodiments.The subject matter disclosed is capable of considerable modifications,alterations, combinations, and equivalents in form and function, as willoccur to one having ordinary skill in the art and having the benefit ofthis disclosure.

FIG. 1 is a flow chart of anon-limiting example method for producingthermoplastic particulates in accordance with the present disclosure.

FIG. 2A shows photographs of Samples 1-9 after UV irradiation at 254 nm.FIG. 2B shows corresponding photographs of Samples 1-9 after UVirradiation and heat treatment at 50° C.

FIG. 3A shows photographs of Samples 10-18 after UV irradiation at 254nm. FIG. 3B shows corresponding photographs of Samples 10-18 after UVirradiation, followed by heat treatment at 50° C. or 150° C.

FIG. 4A is a plot of colorspace lightness (L*) for Samples 1, 2 and 3 asa function of irradiation time. FIG. 4B is a plot of colorspacelightness (L*) for Samples 6, 7 and 8 as a function of irradiation time.FIGS. 5A and 5B are the corresponding plots of colorspace blue/yellowvalue (b*) as a function of irradiation time.

FIG. 6 is a plot of colorspace lightness (L*) for Samples 1, 4, 5, 6 and9 as a function of irradiation time.

FIG. 7 is the corresponding plot of colorspace blue/yellow value (b*) asa function of irradiation time.

FIG. 8 is a plot of colorspace lightness (L*) for Samples 10-18 as afunction of heating temperature.

FIGS. 9 and 10 show plots of colorspace green/red value (a*) andcolorspace blue/yellow value (b*), respectively, for Samples 10-18 as afunction of heating temperature.

DETAILED DESCRIPTION

The present disclosure generally relates to additive manufacturing, andmore particularly, additive manufacturing processes employing powderparticulates that are color changeable during or after forming a printedobject.

As discussed above, printed objects may be formed in a variety ofcomplex shapes through sintering of powder particulates (e.g., throughselective laser sintering and other powder bed fusion processes). Insome instances, it may be desirable to form printed objects having thesame shape but in different colors and/or having multiple colors withina single printed object. At present, both approaches necessitatestockpiling multiple types of powder particulates bearing a specifiedcolorant, which may be costly and operationally complicated in terms ofinventory management and supplying suitable powder particulates to athree-dimensional printing system at a particular time.

The present disclosure demonstrates that color-changing materials may besuccessfully incorporated within powder particulates, particularlycolor-changing materials that are both photochromic and thermochromic.As used herein, the term “photochromic” refers to a substance thatundergoes a color change in the presence of a specified type ofelectromagnetic radiation, and the term “thermochromic” refers to asubstance that undergoes a color change under thermal activation at aspecified temperature. Advantageously, such color-changing materials maybe incorporated within powder particulates following particulatesynthesis by a suitable technique, thereby allowing unmodifiedparticulates to be stockpiled and loaded with a color-changing materialas needed. Particular color-changing materials may be incorporatedwithin powder particulates in response to specific coloration needs.Color-changing materials that are both photochromic and thermochromicare discussed in further detail below.

Advantageous powder particulates may be formed through meltemulsification of a thermoplastic polymer in a high-boiling inertsolvent, particularly in the presence of nanoparticles. U.S. patentapplication Ser. No. 16/946,622, filed on Jun. 30, 2020 and incorporatedherein by reference, provides powder particulates formed by meltemulsification of a thermoplastic polymer in the presence ofnanoparticles, particularly silica nanoparticles or other oxidenanoparticles, which may be especially advantageous in terms of theirnarrow particle size distribution, ready sinterability, and good powderflow performance. Additional details directed to melt emulsificationpreparation of powder particulates in the presence of nanoparticles isprovided hereinbelow.

Surprisingly, a color-changing material may be incorporated upon powderparticulates formed by melt emulsification without compromising theforegoing desirable properties. In particular, one or more conjugateddiynes (also referred to herein as diacetylenes) may be incorporatedupon powder particulates comprising a thermoplastic polymer throughsolution-based treatment of the powder particulates following theirsynthesis by melt emulsification. Many diynes have characteristicphotochromic and thermochromic properties and may be suitable for use inthe disclosure herein, particularly diyne carboxylic acids. Oneparticularly advantageous diyne carboxylic acid suitable for use in thedisclosure herein is 10,12-pentacosadiynoic acid (Formula 1),

which upon photoirradiation and/or thermal activation may afford a blue,red, or yellow coloration to a printed object. Advantageously, theseprimary colors may be blended to produce a variety of secondary colors(e.g., orange, purple and green). As such, the present disclosureprovides access to a much wider array of colors than those directlyobtainable by photoirradiation or thermal activation as provided herein.

Diynes are usually colorless (clear or white) prior to undergoingactivation, either by photoirradiation, heating, or exposure to actinicradiation. Without being bound by theory, photoactivation conditions fordiynes are believed to result in formation of a polymerized reactionproduct that is a diacetylene polymer having a conjugated ene-ynebackbone. Formula 2 shows a structure of a diacetylene polymer believedto result from activation of 10,12-pentacosadiynoic acid (Formula 1)under photoirradiation conditions.

Advantageously, the activation conditions for producing coloration fromconjugated diynes either already occurs during powder bed fusion andsimilar particulate consolidation processes or is readily incorporatedin such processes. Alternately, a printed object containing a conjugateddiyne within a thermoplastic polymer matrix may be readily convertedbetween various coloration states through exposing at least a portion ofthe printed object to appropriate activation conditions. As such,conjugated diynes may be particularly advantageous and compatible forincorporation in additive manufacturing processes.

Although the color-changing performance of conjugated diynes undersuitable activation conditions is known, the present disclosuredemonstrates that unexpected performance may occur when the conjugateddiynes are incorporated upon the surface of thermoplastic particulatescontaining silica nanoparticles. In particular, the intensity of thecolor change may be much more pronounced when activating the conjugateddiyne in the presence of silica nanoparticles. Some tunability of thecoloration and the color intensity may also be realized by changing thefunctionalization, loading, and/or size of the silica nanoparticles.Different surfactants may also impact the intensity of the color change.In addition, the conjugated diyne coloration obtained under variousactivation conditions appears to be permanent in the presence of silicananoparticles, whereas the coloration change for some diynes may fadeonce the activation conditions are removed in the absence of silicananoparticles.

Terms used in the description and claims herein have their plain andordinary meaning, except as modified by the paragraphs below.

As used herein, the term “color-changing material” refers to one or moremonomers that form a colored polymer upon undergoing polymerizationunder specified conditions, and/or a polymer that undergoes a colorchange from a first coloration state to one or more second colorationstates after exposure to specified conditions. The term “color” andgrammatical forms thereof refer to any hue that does not appearcolorless or white when viewed by the human eye.

As used herein, the term “immiscible” refers to a mixture of componentsthat, when combined, form two or more phases that have less than 5 wt. %solubility in each other at ambient pressure and at room temperature orat the melting point of a component if the component is solid at roomtemperature. For example, polyethylene oxide having 10,000 g/molmolecular weight is a solid at room temperature and has a melting pointof 65° C. Therefore, said polyethylene oxide is immiscible with amaterial that is liquid at room temperature if said material and saidpolyethylene oxide have less than 5 wt. % solubility in each other at65° C.

As used herein, the term “thermoplastic polymer” refers to a polymermaterial that softens and hardens reversibly on heating and cooling.Thermoplastic polymers encompass thermoplastic elastomers.

As used herein, the term “nanoparticles” refers to a particulatematerial having a particle size ranging from about 1 nm to about 500 nm.

As used herein, the term “oxide” refers to both metal oxides andnon-metal oxides. For purposes of the present disclosure, silicon isconsidered to be a metal.

As used herein, the term “oxide nanoparticles” refers to a particulatematerial having a particle size ranging from about 1 nm to about 500 nmand comprising a metal oxide or a non-metal oxide.

As used herein, the term “associated” refers to chemical bonding,physical admixture of two or more substances, physical adherence of asubstance to a surface, or any combination thereof, particularly whereinthe substance is an emulsion stabilizer comprising nanoparticles.Without being limited by theory, it is believed that the associationsdescribed herein between polymers and emulsion stabilizers are primarilyphysical adherence via hydrogen bonding and/or other mechanisms.However, chemical bonding may be occurring to some degree. Similarly, acolor-changing material may associate with another substance by one ormore of the foregoing mechanisms.

As used herein, the term “admixed” refers to dissolution of a firstsubstance in a second substance or dispersion of a first substance as asolid in a second substance, wherein the dispersion may be uniform ornon-uniform.

As used herein, the term “D10” refers to a diameter at which 10% of asample (on a volume basis unless otherwise specified) is comprised ofparticles having a diameter less than said diameter value. As usedherein, the term “D50” refers to a diameter at which 50% of a sample (ona volume basis unless otherwise specified) is comprised of particleshaving a diameter less than said diameter value. D50 may also bereferred to as the “average particle size.” As used herein, the term“D90” refers to a diameter at which 90% of a sample (on a volume basisunless otherwise specified) is comprised of particles having a diameterless than said diameter value.

As used herein, the term “shear” refers to stirring or a similar processthat induces mechanical agitation in a fluid.

As used herein, the term “embed,” with respect to nanoparticles and asurface of a polymer particle, refers to the nanoparticles being atleast partially extended into the surface such that polymer is incontact with the nanoparticles to a greater degree than would occur ifthe nanoparticles were simply laid on the surface of the polymerparticle, thereby contacting the surface tangentially.

As used herein, the viscosity of carrier fluids refer to the kinematicviscosity at 25° C., unless otherwise specified, and are measured perASTM D445-19, unless otherwise specified.

The melting point of a thermoplastic polymer, unless otherwisespecified, is determined by ASTM E794-06(2018) with 10° C./min rampingand cooling rates.

The softening temperature or softening point of a thermoplastic polymer,unless otherwise specified, is determined by ASTM D6090-17. Thesoftening temperature can be measured by using a cup and ball apparatusavailable from Mettler-Toledo using a 0.50 gram sample with a heatingrate of 1° C./min.

As used herein, the term “derivative” refers to a compound made directlyor indirectly from another compound, typically in not more than twosynthetic steps.

Particulate compositions of the present disclosure may comprise aplurality of thermoplastic particulates comprising a thermoplasticpolymer, and a color-changing material associated with the thermoplasticparticulates, wherein the color-changing material is both photochromicand thermochromic. In more particular examples, the color-changingmaterial may comprise one or more conjugated diynes, as described infurther detail hereinafter. The particulate compositions disclosedherein may be suitable for use in additive manufacturing processes,particularly additive manufacturing processes employing selective lasersintering and other powder bed fusion processes used to promoteparticulate consolidation. Particulate compositions suitable foradditive manufacturing may exhibit good flow performance fordispensation in a powder bed using a print head or similar device. Flowaids and modifications upon the thermoplastic particulates mayfacilitate the dispensation process. Suitable thermoplastic particulatesmay also exhibit melting and crystallization temperatures compatiblewith a specified consolidation technique in a given additivemanufacturing process.

More specific particulate compositions of the present disclosuresuitable for additive manufacturing may comprise a plurality ofparticulates comprising a thermoplastic polymer, a plurality ofnanoparticles disposed upon an outer surface of each of the plurality ofthermoplastic particulates, and a color-changing material associatedwith the thermoplastic particulates. The color-changing material may beboth photochromic and thermochromic, particularly one or more conjugateddiynes, more particularly one or more conjugated diyne carboxylic acidsor a derivative thereof. Optionally, at least some nanoparticles may beadmixed with the thermoplastic polymer, such that a first portion of thenanoparticles are located within the thermoplastic particulates and asecond portion of the nanoparticles are disposed upon the outer surfaceof the thermoplastic particulates. The nanoparticles disposed upon theouter surface of the thermoplastic particulates may be at leastpartially embedded in the outer surface and associated therewith. Whenpresent, nanoparticles disposed upon the outer surface of thethermoplastic particulates may promote ready dispensation of theparticulate compositions during additive manufacturing.

In some examples, the plurality of nanoparticles may comprise aplurality of oxide nanoparticles. Oxide nanoparticles suitable for usein the present disclosure may include, for example, silicananoparticles, titania nanoparticles, zirconia nanoparticles, aluminananoparticles, iron oxide nanoparticles, copper oxide nanoparticles, tinoxide nanoparticles, boron oxide nanoparticles, cerium oxidenanoparticles, thallium oxide nanoparticles, tungsten oxidenanoparticles, or any combination thereof. Mixed oxides such asaluminosilicates, borosilicates, and aluminoborosilicates, for example,are also encompassed by the term “oxide” and may be suitably used in thedisclosure herein. The oxide nanoparticles may be hydrophilic orhydrophobic in nature, which may be a native property of thenanoparticles or result from surface treatment of the nanoparticles. Forexample, silica nanoparticles having a hydrophobic surface treatment,such as dimethylsilyl, trimethylsilyl, or the like, may be formedthrough reacting hydrophilic surface hydroxyl groups with an appropriatefunctionalizing agent. Hydrophobically modified oxide nanoparticles maybe particularly desirable in the methods and particulate compositions ofthe present disclosure, although unmodified (unfunctionalized) oxidenanoparticles or hydrophilically modified oxide nanoparticles may alsobe suitable for use as well.

Silica nanoparticles, particularly fumed silica nanoparticles with ahydrophobic functionalization thereon, may be especially suitable foruse in the disclosure herein, since a variety of functionalized silicasare available, with the type of hydrophobic functionalization and theparticle size being varied. Hydrophilic fumed silica nanoparticles mayalso be suitably used in the disclosure herein. Silazane and silanehydrophobic functionalizations are among the hydrophobicfunctionalizations that may be used in the present disclosure. As such,the plurality of oxide nanoparticles used in the disclosure herein maycomprise or consist essentially of silica nanoparticles, particularlysilica nanoparticles that are hydrophobically modified orhydrophilically modified. Either type of conjugated diynes may suitablyinteract with conjugated diynes to afford the effects described herein.Silica nanoparticles may be used in combination with another type ofoxide nanoparticle or non-oxide nanoparticle, wherein the other type ofoxide or non-oxide nanoparticle may convey properties to thethermoplastic particulates, or a printed object formed therefrom, thatare not attained when using silica nanoparticles alone.

Carbon black is another type of nanoparticle that may be present uponthermoplastic particulates in the disclosure herein. Various grades ofcarbon black will be familiar to one having ordinary skill in the art,any of which may be used in the disclosure herein. Other nanoparticlescapable of absorbing infrared radiation may be used similarly tofacilitate thermoplastic particulate formation as well. Carbon black,silica, and other types of oxide nanoparticles may be present incombination with one another in some instances. If carbon black isincluded upon the thermoplastic particulates, the loading may be keptsufficiently small to allow the above-described color changes to beobserved.

Polymer nanoparticles are another type of nanoparticle that may bepresent upon thermoplastic particulates in the disclosure herein.Suitable polymer nanoparticles may include one or more polymers that arethermosetting and/or crosslinked, such that they do not melt whenprocessed by melt emulsification or similar particulate formationtechniques according to the disclosure herein. Nanoparticles comprisinghigh molecular weight thermoplastic polymers having high melting ordecomposition points may similarly be suitable for facilitatingparticulate formation from a lower melting thermoplastic polymer.

The loading and particle size of silica nanoparticles or similar oxidenanoparticles upon thermoplastic particulates may vary over a wide rangein the disclosure herein. The loading of the silica nanoparticles orsimilar oxide nanoparticles may be determined by the nanoparticleconcentration in a carrier fluid used to promote formation of thethermoplastic particulates by melt emulsification, as described furtherbelow. Up to about 50 wt. % nanoparticles relative to the thermoplasticpolymer may be present, such as up to about 25 wt. %, or up to about 10wt. %. In non-limiting examples, the concentration of nanoparticles inthe carrier fluid may range from about 0.01 wt. % to about 10 wt. %, orabout 0.05 wt. % to about 10 wt. %, or about 0.05 wt. % to about 5 wt.%, or about 0.1 wt. % to about 2 wt. %, or about 0.25 wt. % to about 1.5wt. %, or about 0.2 wt. % to about 1.0 wt. %, or about 0.25 wt. % toabout 1 wt. %, or about 0.25 wt. % to about 0.5 wt. % with respect tothe weight of the thermoplastic polymer. The particle size of thenanoparticles may range from about 1 nm to about 100 nm, althoughnanoparticle sizes up to about 500 nm may also be acceptable. Innon-limiting examples, the particle size of the nanoparticles may rangefrom about 5 nm to about 75 nm, or about 5 nm to about 50 nm, or about 5nm to about 10 nm, or about 10 nm to about 20 nm, or about 20 nm toabout 30 nm, or about 30 nm to about 40 nm, or about 40 nm to about 50nm, or about 50 nm to about 60 nm. The nanoparticles, particularlysilica nanoparticles and similar oxide nanoparticles, may have a BETsurface area of about 10 m²/g to about 500 m²/g, or about 10 m²/g toabout 150 m²/g, or about 25 m²/g to about 100 m²/g, or about 100 m²/g toabout 250 m²/g, or about 250 m²/g to about 500 m²/g.

Particular silica nanoparticles suitable for use in the disclosureherein may be hydrophobically modified. Hydrophobic functionalizationmay improve dispersion of the silica nanoparticles in a meltemulsification carrier fluid, which may be highly hydrophobic. Thehydrophobic functionalization may be non-covalently or covalentlyattached to a surface of the silica nanoparticles. Covalent attachmentmay take place, for example, through functionalization of surfacehydroxyl groups of the silica nanoparticles. In a non-limiting example,silica nanoparticles may be treated with dichlorodimethylsilane orhexamethyldisilazane to afford covalent attachment of a hydrophobicmodification.

Commercially available hydrophobically functionalized silicananoparticles include, for example, AEROSIL RX50 (Evonik, averageparticle size=40 nm, 25-45 m²/g BET surface area), AEROSIL R812S(Evonik, average particle size=7 nm, 195-245 m²/g BET surface area), andAEROSIL R972 (Evonik, average particle size=16 nm, 90-130 m²/g BETsurface area).

Suitable conjugated diynes that may be incorporated as a color-changingmaterial in the disclosure herein are not considered to be especiallylimited. Illustrative conjugated diynes suitable for use in thedisclosure herein include those described in, for example, U.S. Pat. No.8,063,164 and U.S. Patent Application Publications 2008/0293095 and2020/0199392, each of which is incorporated herein by reference in itsentirety. Conjugated diyne carboxylic acids or derivatives thereof maybe particularly suitable, since long-chain conjugated diyne carboxylicacids are amphiphilic and may organize in micelles. Indeed,preorganization of conjugated diyne carboxylic acids in micelles isusually needed to promote effective polymerization of these molecules.Surprisingly, preorganization of conjugated diynes upon thermoplasticparticulates according to the disclosure herein may also be effective topromote a color-changing polymerization reaction of these types ofmolecules, including those lacking a carboxylic acid head group in someinstances. Examples of long-chain conjugated diyne carboxylic acidssuitable for use in the disclosure herein may have a structurerepresented by Formula 3

wherein R¹ is a C₄-C₂₀ alkyl group with optional branching or heteroatomsubstitution and A is a C₄-C₂₀ alkylene group with optional branching orheteroatom substitution. Preferably, R¹ and A are straight chain alkylor alkylene groups, respectively. In particular examples, R¹ is astraight-chain C₄-C₁₆ alkyl group or a straight-chain C₆-C₁₂ alkyl groupand A is a straight-chain C₄-C₁₆ alkylene group or a straight-chainC₆-C₁₂ alkylene group. In particular examples, R¹ and A may collectivelycontain about 12 carbon atoms to about 36 carbon atoms, or about 16carbon atoms to about 28 carbon atoms, or about 18 carbon atoms to about26 carbon atoms. Particular examples of conjugated diyne carboxylicacids suitable for incorporation upon thermoplastic particulates of thepresent disclosure include, for example, 10,12-pentacosadiynoic acid,4,6-dodecadiynoic acid, 10,12-docosadiynedioic acid, 5,7-eicosadiynoicacid, 10-12-heneicosadiynoic acid, 10-12-heptacosadiynoic acid,5,7-octadecadiynoic acid, 6,8-nonadecadiynoic acid, 5,7-tetradecadiynoicacid, 10-12-tricosadiynoic acid, and any combination thereof.

Derivative forms of conjugated diyne carboxylic acids may also besuitable for use in the disclosure herein. Suitable derivative forms ofconjugated diyne carboxylic acids may include, for example, esters andamides having structures represented by Formulas 4 and 5 below,respectively. Salt forms of the carboxylic acids may also be suitablederivative forms of conjugated

diyne carboxylic acids as well. Esters may serve as suitable precursorsfor conjugated diyne carboxylic acids in some instances. In Formula 4 R²is a C₁-C₂₄ alkyl group with optional branching or heteroatomsubstitution, preferably a C₁-C₁₀ straight-chain or branched alkylgroup. In Formula 5, R³ and R⁴ are independently selected from H and aC₁-C₂₄ alkyl group with optional branching or heteroatom substitution,preferably H or a C₁-C₁₀ straight-chain or branched alkyl group. Aparticular derivative form may be selected to afford a specifiedcoloration following activation of the conjugated diyne and/or toimprove compatibility when incorporating the conjugated diyne upon thethermoplastic particulates. Other diynes that are not carboxylic acidderivatives may also exhibit color-changing properties and may also besuitable for use in the disclosure herein.

Salt form derivatives of conjugated diyne carboxylic acids may similarlybe employed to promote a specified coloration upon activation.Transition metal salts, for example, may attenuate or change the colorformed upon activation of the conjugated diyne. A particular salt formderivative may also be selected to promote solubility or compatibilityin a given solvent when incorporating a conjugated diyne uponthermoplastic particulates, for example. Suitable salt forms of diynecarboxylic acids for use in the disclosure herein may include monovalentmetal salts, such as alkali metal salts; divalent metal salts such asalkaline earth metal salts; trivalent metal salts, such as aluminumsalts; and transition metal salts (e.g., Zn salts).

Alternative color-changing materials may be utilized in place of or incombination with conjugated diyne carboxylic acids. Suitable alternativethermochromic substances may include, for example,bis(2-amino-4-oxo-6-methylpyrimidinium)-tetrachlorocuprate(II);bis(2-amino-4-chloro-6-methylpyrimidinium) hexachlorodicuprate(II);cobalt chloride; 3,5-dinitro salicylic acid; leuco dyes; spiropyrenes,bis(2-amino-4-oxo-6-methylpyrimidinium)tetrachlorocuprate(II) andbis(2-amino-4-chloro-6-methylpyrimidinium) hexachlorodicuprate(II),benzo- and naphthopyrans (chromenes), poly(xylylviologen) dibromide,di-beta-naphthospiropyran, ferrocene-modified bis(spiropyridopyran),isomers of1-isopropylidene-2-[1-(2-methyl-5-phenyl-3-thienyl)ethylidene]-succinicanhydride, infrared dyes, spirobenzopyrans, spironapthooxazines,spirothopyran and related compounds, leucoquinone dyes, naturalleucoquinone, traditional leucoquinone, synthetic quinones, thiazineleuco dyes, acylated leuco thiazine dyes, nonacylated leuco thiazinedyes, oxazine leuco dyes, acylated oxazine dyes, nonacylated oxazineleuco dyes, catalytic dyes, combinations with dye developers,arylmethane phthalides, diarylmethane phthalides, monoarylmethanephthalides, monoheterocyclic substituted phthalides, 3-heterocyclicsubstituted phthalides, diarylmethylazaphthalides, bisheterocyclicsubstituted phthalides, 3,3-bisheterocyclic substituted phthalides,3-heterocyclic substituted azaphthalides, 3,3-bisheterocyclicsubstituted azaphthalides, alkenyl substituted phthalides, 3-ethylenylphthalides, 3,3-bisethylenyl phthalides, 3-butadienyl phthalides,bridged phthalides, spirofluorene phthalides, spirobensanthracenephthalides, bisphthalides, di and triarylmethanes, diphenylmethanes,carbinol bases, fluoran compounds, reaction products of keto acids andphenols, reaction products of keto acids and 4-alkoxydiphenylamines,reaction products of keto acids and 3-alkoxdiphenylamines, reactionproducts of 2′-aminofluorans and aralkyl halides, reaction products of3′-chlorofluorans and amines, tetrazolium salts, tetrazolium salts fromformazans, tetrazolium salts from tetrazoles, and the like.

Other color-changing materials of interest may include, for example,leucodyes, vinylphenylmethane-leucocyanides and derivatives, fluorandyes and derivatives, thermochromic pigments, micro-pigments andnano-pigments, molybdenum compounds, doped or undoped vanadium dioxide,indolinospirochromenes, melting waxes, encapsulated dyes, liquidcrystalline materials, cholesteric liquid crystalline materials,spiropyrans, polybithiophenes, bipyridine materials, mercury chloridedyes, tin complexes, heat formable materials which change structurebased on temperature, natural thermochromic materials such as pigmentsin beans, [Cu(dieten)₂](BF₄)₂ (dieten=N,N-diethylethylenediamine),various thermochromic inks sold by Securink Corp. (Springfield, Va.),Matusui Corp., Liquid Crystal Research Crop., or any acceptablethermochromic materials with the capacity to report a temperature changeor can be photo-stimulated and the like.

Loading of the color-changing material upon the thermoplasticparticulates may vary over a wide range. Depending on the intensity ofthe coloration sought, the loading of the color-changing material may beup to about 50 wt. % relative to the thermoplastic particulates beforeincorporating the color-changing material thereon. In particularexamples, the loading of the color-changing material upon thethermoplastic particulates may range from about 0.1 wt. % to about 50wt. % relative to the thermoplastic polymer, or about 0.5 wt. % to about25 wt. % relative to the thermoplastic polymer, or about 1 wt. % toabout 15 wt. % relative to the thermoplastic polymer, or about 2 wt. %to about 10 wt. % relative to the thermoplastic polymer, or about 5 wt.% to about 25 wt. % relative to the thermoplastic polymer.

Examples of thermoplastic polymers suitable for use in the disclosureherein include, but are not limited to, polyamides (e.g., Nylon-6,Nylon-12, and the like), polyurethanes, polyethylenes, polypropylenes,polyacetals, polycarbonates, polyethylene terephthalates, polybutyleneterephthalates, polystyrenes, polyvinyl chlorides,polytetrafluoroethenes, polyesters (e.g., polylactic acid), polyethers,polyether sulfones, polyetherether ketones, polyacrylates,polymethacrylates, polyimides, acrylonitrile butadiene styrene (ABS),polyphenylene sulfides, vinyl polymers, polyarylene ethers, polyarylenesulfides, polysulfones, polyether ketones, polyaryl ether ketones(PAEK), polyamide-imides, polyetherimides, polyetheresters, copolymerscomprising a polyether block and a polyamide block (PEBA or polyetherblock amide), grafted or ungrafted thermoplastic polyolefins,functionalized or nonfunctionalized ethylene/vinyl monomer polymer,functionalized or nonfunctionalized ethylene/alkyl (meth)acrylates,functionalized or nonfunctionalized (meth)acrylic acid polymers,functionalized or nonfunctionalized ethylene/vinyl monomer/alkyl(meth)acrylate terpolymers, ethylene/vinyl monomer/carbonyl terpolymers,ethylene/alkyl (meth)acrylate/carbonyl terpolymers,methylmethacrylate-butadiene-styrene (MBS)-type core-shell polymers,polystyrene-block-polybutadiene-block-poly(methyl methacrylate) (SBM)block terpolymers, chlorinated or chlorosulphonated polyethylenes,polyvinylidene fluoride (PVDF), phenolic resins, poly(ethylene/vinylacetate)s, polybutadienes, polyisoprenes, styrenic block copolymers,polyacrylonitriles, silicones, and the like, and any combinationthereof. Copolymers comprising one or more of the foregoing may also beused in the present disclosure.

Particularly suitable examples of thermoplastic polymers for use in thedisclosure herein may include polyamides, such as Nylon 6 or Nylon 12;acrylonitrile butadiene styrene; polylactic acid; polyurethanes;poly(arylene ether)s; polyaryletherketones; polycarbonates; polyimides;polyphenylene sulfides; poly(arylene sulfone)s; polyesters, such aspolyethylene terephthalate or polybutylene terephthalate; copolymerscomprising a polyether block and a polyamide block (PEBA or polyetherblock amide); and any combination thereof.

More specific examples of suitable polyamides include, but are notlimited to, polycaproamide (Nylon 6, polyamide 6, or PA6),poly(hexamethylene succinamide) (Nylon 46, polyamide 46, or PA46),polyhexamethylene adipamide (Nylon 66, polyamide 66, or PA66),polypentamethylene adipamide (Nylon 56, polyamide 56, or PA56),polyhexamethylene sebacamide (Nylon 610, polyamide 610, or PA610),polyundecaamide (Nylon 11, polyamide 11, or PA11), polydodecaamide(Nylon 12, polyamide 12, or PA12), and polyhexamethylene terephthalamide(Nylon 6T, polyamide 6T, or PA6T), Nylon 10.10 (polyamide 10.10 orPA10.10), Nylon 10.12 (polyamide 10.12 or PA10.12), Nylon 10.14(polyamide 10.14 or PA10.14), Nylon 10.18 (polyamide 10.18 or PA10.18),Nylon 6.10 (polyamide 6.10 or PA6.10), Nylon 6.18 (polyamide 6.18 orPA6.18), Nylon 6.12 (polyamide 6.12 or PA6.12), Nylon 6.14 (polyamide6.14 or PA6.14), semi-aromatic polyamide, and the like, and anycombination thereof. Copolyamides may also be used. Examples of suitablecopolyamides include, but are not limited to, PA 11/10.10, PA 6/11, PA6.6/6, PA 11/12, PA 10.10/10.12, PA 10.10/10.14, PA 11/10.36, PA11/6.36, PA 10.10/10.36, and the like, and any combination thereof.Polyesteramides, polyetheresteramides, polycarbonate-esteramides, andpolyether block amides, which may be elastomeric, may also be used.

Examples of suitable polyurethanes include, but are not limited to,polyether polyurethanes, polyester polyurethanes, mixed polyether andpolyester polyurethanes, the like, and any combination thereof. Examplesof suitable polyurethanes include, but are not limited to, poly[4,4′-methylenebis(phenylisocyanate)-alt-1,4-butanediol/di(propyleneglycol)/polycaprolactone], ELASTOLLAN® 1190A (a polyether polyurethaneelastomer, available from BASF), ELASTOLLAN® 1190A10 (a polyetherpolyurethane elastomer, available from BASF), and the like, and anycombination thereof.

Suitable thermoplastic polymers may be elastomeric or non-elastomeric.Some of the foregoing examples of thermoplastic polymers may beelastomeric or non-elastomeric depending on the specific composition ofthe polymer. For example, polyethylene that is a copolymer of ethyleneand propylene may be elastomeric or not depending on the amount ofpropylene present in the polymer.

Elastomeric thermoplastic polymers generally fall within one of sixclasses: styrenic block copolymers, thermoplastic polyolefin elastomers,thermoplastic vulcanizates (also referred to as elastomeric alloys),thermoplastic polyurethanes, thermoplastic copolyesters, andthermoplastic polyamides (typically block copolymers comprisingpolyamide), any of which may be used in the disclosure herein. Examplesof elastomeric thermoplastic polymers can be found in Handbook ofThermoplastic Elastomers, 2nd ed., B. M. Walker and C. P. Rader, eds.,Van Nostrand Reinhold, New York, 1988. Examples of elastomericthermoplastic polymers include, but are not limited to, elastomericpolyamides, polyurethanes, copolymers comprising a polyether block and apolyamide block (PEBA or polyether block amide), methylmethacrylate-butadiene-styrene (MBS)-type core-shell polymers,polystyrene-block-polybutadiene-block-poly(methyl methacrylate) (SBM)block terpolymers, polybutadienes, polyisoprenes, styrenic blockcopolymers, and polyacrylonitriles), silicones, and the like.Elastomeric styrenic block copolymers may include at least one blockselected from the group of isoprene, isobutylene, butylene,ethylene/butylene, ethylene-propylene, and ethylene-ethylene/propylene.More specific elastomeric styrenic block copolymer examples include, butare not limited to, poly(styrene-ethylene/butylene),poly(styrene-ethylene/butylene-styrene),poly(styrene-ethylene/propylene), styrene-ethylene/propylene-styrene),poly(styrene-ethylene/propylene-styrene-ethylene-propylene),poly(styrene-butadiene-styrene),poly(styrene-butylene-butadiene-styrene), and the like, and anycombination thereof.

In non-limiting examples, thermoplastic particulates of the disclosureherein may be formed through melt emulsification. Such methods forproducing thermoplastic particulates may comprise combining athermoplastic polymer in a carrier fluid at a heating temperature at orabove a melting point or softening temperature of the thermoplasticpolymer, wherein the thermoplastic polymer and the carrier fluid aresubstantially immiscible at the heating temperature; applying sufficientshear to disperse the thermoplastic polymer as liquefied droplets in thecarrier fluid at the heating temperature; after liquefied droplets haveformed, cooling the carrier fluid to at least a temperature at whichthermoplastic particulates in a solidified state form, the thermoplasticparticulates comprising the thermoplastic polymer; and separating thethermoplastic particulates from the carrier fluid. More specificexamples of such methods may comprise combining a thermoplastic polymerand nanoparticles in a carrier fluid at a heating temperature at orabove a melting point or softening temperature of the thermoplasticpolymer; wherein the thermoplastic polymer and the carrier fluid aresubstantially immiscible at the heating temperature; applying sufficientshear to disperse the thermoplastic polymer as liquefied droplets in thecarrier fluid at the heating temperature; after liquefied droplets haveformed, cooling the carrier fluid to at least a temperature at whichthermoplastic particulates in a solidified state form, the thermoplasticparticulates comprising the thermoplastic polymer and at least a portionof the nanoparticles associated with an outer surface of each of thethermoplastic particulates; and separating the thermoplasticparticulates from the carrier fluid. Suitable examples of thermoplasticpolymers and nanoparticles are provided hereinabove, any of which may beused for forming the thermoplastic particulates according to thedisclosure herein. Once formed through melt emulsification, thethermoplastic particulates may be further processed to introduce thecolor-changing material, as described in further detail below.

FIG. 1 is a flow chart of non-limiting example method 100 for producingthermoplastic particulates in accordance with the present disclosure,wherein particulate formation takes place in the presence ofnanoparticles. As shown, thermoplastic polymer 105, carrier fluid 104and nanoparticles 106 are combined 108 to produce mixture 110. One ormore surfactants, such as one or more sulfonate surfactants, may also bepresent in mixture 110. When present, up to about 25 wt. % surfactantrelative to thermoplastic polymer 105 may be present in mixture 110.Thermoplastic polymer 105, carrier fluid 104, and nanoparticles 106 maybe combined 108 in any order, with mixing and/or heating beingconducted. In a particular example, carrier fluid 104 may be heatedabove a melting point or softening temperature of thermoplastic polymer105 before combining the other components therewith.

Heating above the melting point or softening temperature ofthermoplastic polymer 105 may be at any temperature below thedecomposition temperature or boiling point of any of the components inthe melt emulsion. In non-limiting examples, heating at a temperatureabout 1° C. to about 50° C., or about 1° C. to about 25° C., or about 5°C. to about 30° C., or about 20° C. to about 50° C. above the meltingpoint or softening temperature of thermoplastic polymer 105 may beconducted. In the disclosure herein, melting points may be determined byASTM E794-06(2018) with 10° C./min ramping and cooling rates. Thesoftening temperature or softening point of a polymer, unless otherwisespecified, is determined by ASTM D6090-17. The softening temperature canbe measured by using a cup and ball apparatus available fromMettler-Toledo using a 0.50 gram sample with a heating rate of 1°C./min. Melting points or softening temperatures in the presentdisclosure may range from about 50° C. to about 400° C., or about 60° C.to about 300° C.

Mixture 110 is then processed 112 by applying sufficient shear toproduce liquefied droplets of thermoplastic polymer 105 at a temperaturegreater than the melting point or softening temperature of thermoplasticpolymer 105, thereby forming melt emulsion 114. Without being limited bytheory, it is believed that, all other factors being the same,increasing shear may decrease the size of the liquefied droplets incarrier fluid 104. It is to be understood that at some point there maybe diminishing returns on increasing shear and decreasing the dropletsize in turn and/or disruptions to the droplet contents at higher shearrates. Examples of mixing apparatuses suitable for producing meltemulsion 114 include, but are not limited to, extruders (e.g.,continuous extruders, batch extruders and the like), stirred reactors,blenders, reactors with inline homogenizer systems, and the like, andapparatuses derived therefrom.

In non-limiting examples, the liquefied droplets may have a size ofabout 1 μm to about 1,000 μm, or about 1 μm to about 500 μm, or about 1μm to about 200 μm, or about 1 μm to about 150 μm, or about 1 μm toabout 130 μm, or about 1 μm to about 100 μm, or about 10 μm to about 150μm, or about 10 μm to about 100 μm, or about 20 μm to about 80 μm, orabout 20 μm to about 50 μm, or about 50 μm to about 90 μm. The resultingthermoplastic particulates formed after solidification may reside withinsimilar size ranges. That is, the thermoplastic particulates in theparticulate compositions and methods of the present disclosure may havea size of about 1 μm to about 1,000 μm, or about 1 μm to about 500 μm,or about 1 μm to about 200 μm, or about 1 μm to about 150 μm, or about 1μm to about 130 μm, or about 1 μm to about 100 μm, or about 1 μm toabout 200 μm, or about 10 μm to about 100 μm, or about 20 μm to about 80μm, or about 20 μm to about 50 μm, or about 50 μm to about 90 μm.Particle size measurements may be made by analysis of optical images orusing onboard software of a Malvern Mastersizer 3000 Aero S instrument,which uses light scattering techniques for particle size measurement.The foregoing particulate sizes may be maintained after incorporating acolor-changing material upon the thermoplastic particulates.

For light scattering techniques, glass bead control samples with adiameter within the range of 15 μm to 150 μm under the tradename QualityAudit Standards QAS4002™ obtained from Malvern Analytical Ltd. may beused. Samples may be analyzed as dry powders dispersed in air using thedry powder dispersion module of the Mastersizer 3000 Aero S. Particlesizes may be derived using the instrument software from a plot of volumedensity as a function of size.

Melt emulsion 114 is then cooled 116 to solidify the liquefied dropletsinto thermoplastic particulates in a solidified state. The cooling ratemay range from about 100° C./sec to about 10° C./hour or about 10°C./sec to about 10° C./hr, including any cooling rate in between. Shearmay be discontinued during cooling, or may be maintained at the samerate or a different rate during cooling. Cooled mixture 118 can then betreated 120 to isolate thermoplastic particulates 126 from othercomponents 124 (e.g., carrier fluid 104, excess nanoparticles 106, andthe like). Washing, filtering and/or the like may be conducted at thisstage to purify thermoplastic particulates 122 further, whereinthermoplastic particulates 122 comprise thermoplastic polymer 105, andat least a portion of nanoparticles 106 coating the outer surface ofthermoplastic particulates 122 as at least a partial coating. Dependingupon non-limiting factors such as the temperature (including coolingrate), the type of thermoplastic polymer 105, and the types and sizes ofnanoparticles 106, nanoparticles 106 may become at least partiallyembedded within the outer surface of thermoplastic particulates 122 inthe course of becoming disposed thereon. Even without embedment takingplace, nanoparticles 106 may remain robustly associated withthermoplastic particulates 122 to facilitate their further use.

In the foregoing, thermoplastic polymer 105 and carrier fluid 104 arechosen such that these components are immiscible or substantiallyimmiscible (<5 wt. % solubility), particularly <1 wt. % solubility, atthe various processing temperatures (e.g., from room temperature to thetemperature at which liquefied droplets are formed and maintained as twoor more phases).

After separating thermoplastic particulates 122 from other components124, further processing 126 of thermoplastic particulates 122 may takeplace. In a non-limiting example further processing 126 may include, forexample, sieving thermoplastic particulates 122 and/or blendingthermoplastic particulates 122 with other substances to form processedthermoplastic particulates 128. Processed thermoplastic particulates 128may be formulated for use in a desired application, such as additivemanufacturing in a non-limiting example.

In another non-limiting example, further processing 126 may compriseincorporating the color-changing material, such as one or moreconjugated diynes, upon thermoplastic particulates 122. Optionally, asurfactant (e.g., an anionic surfactant, a cationic surfactant, aneutral surfactant, or a zwitterionic surfactant) may be incorporatedupon thermoplastic particulates 122 as well during further processing126. Additional details concerning incorporation of a color-changingmaterial upon thermoplastic particulates 122 are provided hereinbelow.

The thermoplastic particulates of the present disclosure may have a bulkdensity of about 0.3 g/cm³ to about 0.8 g/cm³, or about 0.3 g/cm³ toabout 0.6 g/cm³, or about 0.4 g/cm³ to about 0.7 g/cm³, or about 0.5g/cm³ to about 0.6 g/cm³, or about 0.5 g/cm³ to about 0.8 g/cm³.

Shear sufficient to form liquefied droplets may be applied throughstirring the carrier fluid in particular examples of the presentdisclosure. In non-limiting examples, the stirring rate may range fromabout 50 rotations per minute (rpm) to about 1500 rpm, or about 250 rpmto about 1000 rpm, or about 225 rpm to about 500 rpm. The stirring ratewhile melting or softening the thermoplastic polymer may be the same asor different than the stirring rate used once liquefied droplets haveformed. The liquefied droplets may be stirred over a stirring time ofabout 30 seconds to about 18 hours or longer, or about 1 minute to about180 minutes, or about 1 minute to about 60 minutes, or about 5 minutesto about 6 minutes, or about 5 minutes to about 30 minutes, or about 10minutes to about 30 minutes, or about 30 minutes to about 60 minutes.

Loading (concentration) of the thermoplastic polymer in the carrierfluid may vary over a wide range. In non-limiting examples, the loadingof the thermoplastic polymer in the carrier fluid may range from about 1wt. % to about 99 wt. % relative to the weight of the carrier fluid. Inmore particular examples, the loading of the thermoplastic polymer mayrange from about 5 wt. % to about 75 wt. %, or about 10 wt. % to about60 wt. %, or about 20 wt. % to about 50 wt. %, or about 20 wt. % toabout 30 wt. %, or about 30 wt. % to about 40 wt. %, or about 40 wt. %to about 50 wt. %, or about 50 wt. % to about 60 wt. %. Thethermoplastic polymer may be present in an amount ranging from about 5wt. % to about 60 wt. %, or about 5 wt. % to about 25 wt. %, or about 10wt. % to about 30 wt. %, or about 20 wt. % to about 45 wt. %, or about25 wt. % to about 50 wt. %, or about 40 wt. % to about 60 wt. % relativeto a combined amount of the thermoplastic polymer and the carrier fluid.

Upon forming thermoplastic particulates in the presence of nanoparticlesaccording to the disclosure herein, at least a portion of thenanoparticles, such as silica nanoparticles or other oxidenanoparticles, may be disposed as a coating or partial coating upon theouter surface of the thermoplastic particulates. The coating may bedisposed substantially uniformly upon the outer surface. As used hereinwith respect to a coating, the term “substantially uniform” refers to aneven coating thickness in surface locations covered by thenanoparticles, particularly the entirety of the outer surface. Coatingcoverage upon the thermoplastic particulates may range from about 5% toabout 100%, or about 5% to about 25%, or about 20% to about 50%, orabout 40% to about 70%, or about 50% to about 80%, or about 60% to about90%, or about 70% to about 100% of the surface area of the particulates.Coverage may be determined by image analysis of SEM micrographs.

Carrier fluids suitable for use in the disclosure herein include thosein which the thermoplastic polymer is substantially immiscible with thecarrier fluid, the carrier fluid has a boiling point exceeding themelting point or softening temperature of the thermoplastic polymer, andthe carrier fluid has sufficient viscosity to form liquefied droplets ofsubstantially spherical shape once the thermoplastic polymer hasundergone melting therein. Suitable carrier fluids may include, forexample, silicone oil, fluorinated silicone oils, perfluorinatedsilicone oils, polyethylene glycols, alkyl-terminal polyethylene glycols(e.g., C1-C4 terminal alkyl groups like tetraethylene glycol dimethylether (TDG)), paraffins, liquid petroleum jelly, vison oils, turtleoils, soya bean oils, perhydrosqualene, sweet almond oils, calophyllumoils, palm oils, parleam oils, grapeseed oils, sesame oils, maize oils,rapeseed oils, sunflower oils, cottonseed oils, apricot oils, castoroils, avocado oils, jojoba oils, olive oils, cereal germ oils, esters oflanolic acid, esters of oleic acid, esters of lauric acid, esters ofstearic acid, fatty esters, higher fatty acids, fatty alcohols,polysiloxanes modified with fatty acids, polysiloxanes modified withfatty alcohols, polysiloxanes modified with polyoxy alkylenes, the like,and any combination thereof.

Suitable carrier fluids may have a density of about 0.6 g/cm³ to about1.5 g/cm³, and the thermoplastic polymer may have a density of about 0.7g/cm³ to about 1.7 g/cm³, wherein the thermoplastic polymer has adensity similar to, lower than, or higher than the density of thecarrier fluid.

Particularly suitable silicone oils are polysiloxanes. Illustrativesilicone oils suitable for use in the disclosure herein include, forexample, polydimethylsiloxane (PDMS), methylphenylpolysiloxane, an alkylmodified polydimethylsiloxane, an alkyl modifiedmethylphenylpolysiloxane, an amino modified polydimethylsiloxane, anamino modified methylphenylpolysiloxane, a fluorine modifiedpolydimethylsiloxane, a fluorine modified methylphenylpolysiloxane, apolyether modified polydimethylsiloxane, a polyether modifiedmethylphenylpolysiloxane, the like and any combination thereof.

In non-limiting examples, the carrier fluid and the thermoplasticpolymer may be heated at a temperature of about 200° C. or above.Suitable heating temperatures may be chosen based upon the melting pointor softening temperature of the thermoplastic polymer and the boilingpoint of the carrier fluid. A maximum heating temperature may be limitedby the decomposition point of the carrier fluid and/or the thermoplasticpolymer, but in many instances the maximum heating temperature may be upto about 300° C., preferably up to about 260° C. The cooling ratefollowing formation of liquefied polymer droplets may be varied asdesired. In some instances, cooling may take place with heat dissipationto the surrounding environment taking place at an innate (uncontrolled)rate once heating is discontinued. In other cases, cooling at acontrolled rate (e.g., by gradually decreasing the heating temperatureand/or using jacketed temperature control to increase or decrease therate of cooling may be employed.

Suitable carrier fluids, such as polysiloxanes, including PDMS, may havea viscosity at 25° C. of about 1,000 cSt to about 150,000 cSt, or about1,000 cSt to about 60,000 cSt, or about 40,000 cSt to about 100,000 cSt,or about 75,000 cSt to about 150,000 cSt. The viscosity of the carrierfluid may be obtained from commercial suppliers or it may be measured,if desired, through techniques known to persons having ordinary skill inthe art.

Separating the thermoplastic particulates from the carrier fluid maytake place by any of a variety of known separation techniques. Any ofgravity settling and filtration, decantation, centrifugation, or thelike may be used to separate the thermoplastic particulates from thecarrier fluid. The thermoplastic particulates may then be washed with asolvent in which the carrier fluid is soluble and the thermoplasticparticulates are insoluble in the course of the separation process. Inaddition, a solvent in which the carrier fluid is soluble and thethermoplastic particulates are insoluble may be mixed with the carrierfluid and the thermoplastic particulates before initially separating theelastomeric particulates from the carrier fluid. The solvent and/or thecarrier fluid may be recycled for processing subsequent batches ofthermoplastic particulates, if desired.

Suitable solvents for washing the thermoplastic particulates or mixingwith the carrier fluid may include, but are not limited to, aromatichydrocarbons (e.g., toluene and/or xylene), aliphatic hydrocarbons(e.g., heptane, n-hexane, and/or n-octane), cyclic hydrocarbons (e.g.,cyclopentane, cyclohexane, and/or cyclooctane), ethers (e.g. diethylether, tetrahydrofuran, diisopropyl ether, and/or dioxane), halogenatedhydrocarbons (e.g., dichloroethane, trichloroethane, dichloromethane,chloroform and/or carbon tetrachloride), alcohols (e.g., methanol,ethanol, isopropanol, and/or n-propanol), ketones (e.g., methyl ethylketone and/or acetone); esters (e.g., ethyl acetate and the like),water, the like, and any combination thereof. After washing thethermoplastic particulates, any of heating, vacuum drying, air drying,or any combination thereof may be performed to remove residual solvent.

At least a majority of the thermoplastic particulates obtained accordingto the disclosure here may be substantially spherical in shape. Moretypically, about 90% or greater, or about 95% or greater, or about 99%or greater of the thermoplastic particulates produced by meltemulsification according to the present disclosure may be substantiallyspherical in shape. In other non-limiting examples, the thermoplasticparticulates of the present disclosure may have a sphericity(circularity) of about 0.9 or greater, including about 0.90 to about1.0, or about 0.93 to about 0.99, or about 0.95 to about 0.99, or about0.97 to about 0.99, or about 0.98 to 1.0. Sphericity (circularity) maybe measured using a Sysmex FPIA-2100 Flow Particle Image Analyzer. Todetermine circularity, optical microscopy images are taken of theparticulates. The perimeter (P) and area (A) of the particulates in theplane of the microscopy image is calculated (e.g., using a SYSMEX FPIA3000 particle shape and particle size analyzer, available from MalvernInstruments). The circularity of the particulate is CEA/P, where CEA isthe circumference of a circle having the area equivalent to the area (A)of the actual particulate.

The thermoplastic particulates of the present disclosure may have anangle of repose of about 25° to about 45°, or about 25° to about 35°, orabout 30° to about 40°, or about 35° to about 45°. Angle of repose maybe determined using a Hosokawa Micron Powder Characteristics Tester PT-Rusing ASTM D6393-14 “Standard Test Method for Bulk Solids” Characterizedby Carr Indices.”

Thermoplastic particulates isolated from the carrier fluid according tothe disclosure above may be further processed to make the thermoplasticparticulates suitable for an intended application. In one example, thethermoplastic particulates may be passed through a sieve or similarstructure having an effective screening size that is greater than theaverage particle size of the thermoplastic particulates. For example, anillustrative screening size for processing thermoplastic particulatessuitable for use in three-dimensional printing may have an effectivescreening size of about 150 μm. When referring to sieving, pore/screensizes are described per U.S.A. Standard Sieve (ASTM E11-17). Otherscreening sizes, either larger or smaller, may be more suitable forthermoplastic particulates destined for use in other applications.Sieving may remove larger particulates that may have formed during themelt emulsification process and/or remove agglomerated particulates thatmay have poor flow characteristics. In general, sieves having aneffective screening size ranging from about 10 μm to about 250 μm may beused.

In another particular example, further processing the thermoplasticparticulates may comprise associating a color-changing material with thethermoplastic particulates following their formation under meltemulsification conditions, as described above. The color-changingmaterial, such as a conjugated diyne, may be dissolved or suspended in asolvent and then contacted with the thermoplastic particulates. Suitablesolvents may be chosen such that they do not appreciably swell thethermoplastic particulates or otherwise impact their powder flowperformance. In a non-limiting example, the color-changing material maybe dissolved or suspended in the same solvent used for washing thethermoplastic particulates following their synthesis through meltemulsification or in a similar type of solvent, such as heptane or asimilar saturated hydrocarbon solvent.

Contacting the thermoplastic particulates and the color-changingmaterial in the solvent may take place under static or non-staticconditions at a temperature ranging from about 0° C. up to the refluxtemperature of the solvent. Preferably, contacting may take place atroom temperature. Non-static contacting conditions may include stirring,sonication, or any combination thereof. Contacting times forincorporating the color-changing material upon the thermoplasticparticulates may range from about 1 minute to about 24 hours, or about10 minutes to about 12 hours, or about 30 minutes to about 6 hours, orabout 1 hour to about 4 hours, or about 6 hours to about 12 hours.

After the color-changing material has been suitably associated with thethermoplastic particulates, the thermoplastic particulates may beisolated from the solvent, such as through filtration, decantation,centrifugation, or any combination thereof. Drying of the thermoplasticparticulates may then take place before use.

In addition, the thermoplastic particulates, after having thecolor-changing material associated therewith, may be mixed with one ormore additional components such as flow aids, fillers or othersubstances intended to tailor the properties of the thermoplasticparticulates for an intended application. Mixing of the additionalcomponents with the thermoplastic particulates may be conducted by dryblending techniques. The additional components may be included in anamount such that the above-described color change remains observable.Suitable examples of flow aids (e.g., carbon black, graphite, silica,and the like) and similar substances will be familiar to one havingordinary skill in the art. Additional sieving of the thermoplasticparticulates may also take place at this stage and/or after associationof the color-changing material, if needed.

In particular applications, the particulate compositions disclosedherein may be utilized in additive manufacturing processes, especiallythose employing selective laser sintering or other powder bed fusionprocesses to promote particulate consolidation.

Depending on how particulate consolidation is performed, a printedobject formed through particulate consolidation of thermoplasticparticulates bearing a color-changing material may be colorless (i.e.,have a coloration determined primarily by the thermoplastic polymer) orbe in a first coloration state determined primarily by thecolor-changing material, and possibly enhanced by the presence ofnanoparticles. For example, in the case of a conjugated diyne such as10,12-pentacosadiynoic acid, a printed object obtained throughparticulate consolidation with an infrared laser (e.g., a CO₂ laser orsimilar infrared or near-infrared laser) may leave the conjugated diyneinitially unactivated and the printed object in a substantiallycolorless state. Thereafter, the conjugated diyne may be activatedthrough ultraviolet photoirradiation to promote polymerization of theconjugated diyne into a diacetylene polymer, which may afford a firstcoloration state to the printed object. In the case of10,12-pentacosaidynoic acid and similar conjugated diynoic acids, thefirst coloration state may be blue or a blue shade. The complete printedobject may be converted to the first coloration state throughirradiating the entirety of the outer surface of the printed object, orthe first coloration may be introduced selectively upon the printedobject, such as through localized UV irradiation of specified positionsupon the surface of the printed object.

After forming the first coloration state, a second coloration state maybe introduced into the printed object through thermal treatment. Thesecond coloration state may be reached by heating the printed object toa temperature ranging from about 30° C. to about 200° C. In the case of10,12-pentacosadiynoic acid, the second coloration state may be a red tomagenta color attained by heating the printed object to about 50° C., orthe second coloration state may be yellow or a yellow shade by heatingthe printed object to about 150° C. The entirety of the outer surface ofthe printed object may be converted to the second coloration state, orthe second coloration state may be introduced selectively throughlocalized heating. Alternately, after producing the second colorationstate, any of the conjugated diyne not previously converted to the firstcoloration state may converted to the first coloration state through UVirradiation. Thus, in some instances it is possible for the firstcoloration state and the second coloration state to be co-present incombination with one another in a printed object, in addition tocolorless areas in which the color-changing material has not beenactivated. In addition, for any areas produced in the first colorationstate after already producing the second coloration state, the newlyproduced first coloration state may be converted to a second colorationstate that is the same as or different than that produced previously.For example, a printed object having a yellow second coloration statemay be produced in combination with a blue first coloration statethrough subsequent activation of a conjugated diyne. Thereafter, theblue first coloration state may be activated to produce a red or magentasecond coloration state. Thus, depending on particular applicationneeds, a wide range of color combinations may be attainable.

Accordingly, additive manufacturing processes of the present disclosuremay afford printed objects having a polymer matrix comprising athermoplastic polymer, and a color-changing material associated with thepolymer matrix, wherein the color-changing material is both photochromicand thermochromic. The color-changing material may comprise one or moreconjugated diynes or a polymerized form thereof, wherein the polymerizedform may afford a first coloration state and/or a second colorationstate different from the first coloration state to at least a portion ofthe printed object. For example, in at least a portion of a printedobject, at least a majority of one or more conjugated diynes may bepresent as the polymerized form and convey a first coloration state tothe portion of the printed object. The polymerized form may be modifiedby heating such that the portion of the printed object has a secondcoloration state different than the first coloration state in at least aportion of the printed object.

A plurality of nanoparticles may also be present within the polymermatrix, such as a plurality of silica nanoparticles or other types ofoxide nanoparticles. Advantageously, silica nanoparticles may intensifythe coloration obtained from the first coloration state and/or thesecond coloration state. A surfactant may also be present within thepolymer matrix as well.

Additive manufacturing processes of the present disclosure may compriseproviding a particulate composition comprising a plurality ofthermoplastic particulates comprising a thermoplastic polymer, and acolor-changing material associated with the thermoplastic particulates,wherein the color-changing material is both photochromic andthermochromic, and forming a printed object having a polymer matrixcomprising the thermoplastic polymer and the color-changing materialassociated with the polymer matrix. Preferably, the thermoplasticparticulates have a plurality of nanoparticles, such as silicananoparticles or other oxide nanoparticles, disposed upon an outersurface of the thermoplastic particulates, such that the silicananoparticles or other oxide nanoparticles are present within thepolymer matrix upon forming a printed object. In more particularexamples, methods for forming a printed object according to the presentdisclosure may comprise depositing the particulate composition in apowder bed, and consolidating a portion of the thermoplasticparticulates in the powder bed.

Methods for forming a printed object according to the present disclosuremay comprise introducing coloration to the printed object. Inparticular, methods of the present disclosure may comprise exposing atleast a portion of the printed object to first activation conditions,such as photoirradiation (e.g., UV irradiation), sufficient to convertthe color-changing material into a polymerized form of thecolor-changing material having a first coloration state. Thereafter, asneeded, methods of the present disclosure may comprise exposing at leasta portion of the printed object to second activation conditions, such asthermal activation, sufficient to convert the polymerized form of thecolor-changing material into a second coloration state different fromthe first coloration state. The first coloration state and the secondcoloration state may be present together in a given printed objectthrough localized application of the first and second activationconditions.

Suitable conditions for performing selective laser sintering or otherpowder bed particulate consolidation processes to form a printed objectare not believed to be especially limited. Depending on the desiredoutcome, the particulate consolidation processes may or may not alsopromote polymerization of the conjugated diyne to produce the firstcoloration state. That is, depending on how particulate consolidation isperformed, the printed object or a portion thereof may be in an initialcoloration state primarily determined by the thermoplastic polymer(e.g., white or colorless), which is then converted to a firstcoloration state determined by a polymerized form of the conjugateddiyne. Lasers suitable for performing selective laser sintering withoutactivating a conjugated diyne may include both continuous wave lasersand pulsed wave lasers, either of which may provide the energy needed topromote consolidation of thermoplastic particulates. CO₂ lasers arecommonly used to promote consolidation of thermoplastic particulatesduring selective laser sintering due to the high absorptivity of thepolymers to the CO₂ laser emission wavelength. The operating conditionsof the CO₂ laser may be chosen such that particulate consolidationoccurs in preference to activation of the conjugated diyne. Standardlaser settings for promoting consolidation of thermoplastic particulates(e.g., power, scanning rate, bed temperature, and the like) may beselected based on the particular thermoplastic polymer that is present,and suitable laser settings may be chosen by one having ordinary skillin the art. The choice of particular conditions for conducting selectivelaser sintering or similar powder consolidation techniques may beinfluenced by non-limiting factors such as, for example, the type ofthermoplastic polymer being used, the size and composition of thethermoplastic particulates, the type of printed object being produced,and the intended use conditions for the printed object.

Heating of at least a portion of a printed object may be conductedradiantly over substantially the entirety of the surface of a printedobject, or heating may be localized such as through directed heating,such as with a laser or heated air flow. Other techniques for producinglocalized heating may also be suitable and will be recognizable to onehaving ordinary skill in the art.

Examples of printed objects formable using the particulate compositionsdisclosed herein are not considered to be particularly limited and mayinclude, for example, containers (e.g., for food, beverages, cosmetics,personal care compositions, medicine, and the like), shoe soles, toys,furniture parts, decorative home goods, plastic gears, screws, nuts,bolts, cable ties, medical items, prosthetics, orthopedic implants,learning aids, 3D anatomy models, robotics, biomedical devices(orthotics), home appliances, dentistry, automotive andairplane/aerospace parts, electronics, sporting goods, and the like. Theability to manufacture these and other types of printed objects in arange of colors may be advantageous, as discussed hereinafter.

In a specific example, the particulate compositions disclosed herein maycomprise at least a portion of an autonomous temperature sensor. Inparticular, a printed object may comprise a patterned location of thecolor-changing material activated to a first coloration state (e.g.,blue in the case of a conjugated diyne). Alternately, a decal or similarlabel comprising a patterned mark of the thermoplastic polymer and thecolor-changing material activated to a first coloration state may beapplied to an existing object, which may be printed or non-printed.Thereafter, further thermal activation of the color-changing materialinto a second coloration state may be indicative of conditions to whichthe object has been exposed.

Embodiments disclosed herein include:

A. Particulate compositions comprising powder particulates. Theparticulate compositions comprise: a plurality of thermoplasticparticulates comprising a thermoplastic polymer, and a color-changingmaterial associated with the thermoplastic particulates, thecolor-changing material being both photochromic and thermochromic.

B. Printed objects. The printed objects comprise: a polymer matrixcomprising a thermoplastic polymer; and a color-changing materialassociated with the polymer matrix, the color-changing material beingboth photochromic and thermochromic.

C. Methods for forming a printed object by particulate consolidation.The methods comprise: providing a particulate composition comprising aplurality of thermoplastic particulates comprising a thermoplasticpolymer, and a color-changing material associated with the thermoplasticparticulates, the color-changing material being both photochromic andthermochromic; and forming a printed object having a polymer matrixcomprising the thermoplastic polymer and the color-changing materialassociated with the polymer matrix.

Each of embodiments A-C may have one or more of the following additionalelements in any combination:

Element 1: wherein the color-changing material comprises one or moreconjugated diynes.

Element 2: wherein the one or more conjugated diynes comprise aconjugated diyne carboxylic acid or a derivative thereof.

Element 3: wherein the conjugated diyne carboxylic acid comprises10,12-pentacosadiynoic acid.

Element 4: wherein the particulate composition further comprises aplurality of nanoparticles disposed upon an outer surface of each of theplurality of thermoplastic particulates, the plurality of nanoparticlescomprising a plurality of oxide nanoparticles.

Element 5: wherein the plurality of oxide nanoparticles comprises aplurality of silica nanoparticles.

Element 6: wherein the silica nanoparticles are hydrophobicallymodified.

Element 7: wherein the particulate compositions further comprise asurfactant associated with an outer surface of the thermoplasticparticulates.

Element 8: wherein the color-changing material comprises one or moreconjugated diynes or a polymerized form thereof.

Element 9: wherein at least a majority of the one or more conjugateddiynes is present as the polymerized form and the printed object has afirst coloration state.

Element 10: wherein the polymerized form is modified by heating and theprinted object has a second coloration state different from the firstcoloration state.

Element 11: wherein the printed object further comprises a plurality ofnanoparticles present within the polymer matrix, the plurality ofnanoparticles comprising a plurality of oxide nanoparticles.

Element 12: wherein the printed object further comprises a surfactantpresent within the polymer matrix.

Element 13: wherein forming the printed object comprises: depositing theparticulate composition in a powder bed; and consolidating a portion ofthe thermoplastic particulates in the powder bed.

Element 14: wherein the method further comprises: exposing at least aportion of the printed object to first activation conditions sufficientto convert the color-changing material into a polymerized form of thecolor-changing material having a first coloration state. Element 15:wherein the first activation conditions comprise photoirradiation of theprinted object.

Element 16: wherein the method further comprises exposing at least aportion of the printed object to second activation conditions sufficientto convert the polymerized form of the color-changing material into asecond coloration state different from the first coloration state.

Element 17: wherein the second activation conditions comprise thermaltreatment of the printed object.

Element 18: wherein the plurality of thermoplastic particulates furthercomprises a plurality of nanoparticles disposed upon an outer surface ofeach of the plurality of thermoplastic particulates, the plurality ofnanoparticles comprising a plurality of oxide nanoparticles.

Element 19: wherein a surfactant is associated with an outer surface ofthe thermoplastic particulates.

By way of non-limiting example, exemplary combinations applicable to Ainclude, but are not limited to: 1 and 4; 1, 2 or 3, and 4; 1-4 and 5;1, 2 or 3, and 4 or 5; 1 and 7; 1, 4 and 7; 1, 2 or 3, 4 and 7; 1-4, 5and 7; 4 and 7; and 4, 5 and 7. Exemplary combinations applicable to Binclude, but are not limited to, 8 and 9; 8-10; 8 and 11; 8, 5 and 11; 8and 12; 8, 11 and 12; 8, 5, 11 and 12; 5 and 11; 5, 11 and 12; and 11and 12. Exemplary combinations applicable to C include, but are notlimited to, 13 and 14; 13-15; 13 and 16; 13, 14 and 16; 13-16; 13, 16and 17; 13-17; any of the foregoing in further combination with 1; 1,and 2 or 3; 18; 19; 18 and 19; 18 and 5; and 18, 5 and 19.

To facilitate a better understanding of the present disclosure, thefollowing examples of preferred or representative embodiments are given.In no way should the following examples be read to limit, or to define,the scope of the invention.

EXAMPLES

Polyether block amide (PEBA, VESTAMID E40S3, polyamide-12, Evonik) wasprocessed into powder particulates through melt emulsification in thefollowing examples. Where noted, silica nanoparticles were includedduring the melt emulsification process.

UV irradiation was performed using a 254 nm short wavelength irradiationlamp (Spectroline Model ENF-260C, Spectronics Corporation). Irradiationwas performed at a 7 cm distance from the sample.

Heating was performed using an IKA RCT basic hot plate set at aspecified temperature.

Sample coloration was determined using a XRITE 528spectrophotodensiometer.

Syntheses

Sample 1: A 500 mL glass reactor was loaded with 160 g silicone oil (PSF10,000, Clearco) and heated to 200° C. under nitrogen at a stirring rateof 500 rpm. VESTAMID E40S3 polymer particles (40 g) were added to thereactor and stirring was continued for an additional 30 minutes. Themixture was then cooled to room temperature, and the resulting polymerparticulates were separated by vacuum filtration on Whatman filterpaper. The polymer particulates were washed 3 times on the filter paperwith heptane.

10,12-Pentacosadiynoic acid was then incorporated with the polymerparticulates. 0.8 g Polymer particulates and 0.2 g10,12-pentacosadiynoic acid were combined in 9 g ethanol, and themixture was stirred at 1000 rpm for 2 hours at room temperature.Sonication was then performed for 1 hour, and the mixture was stored at4° C. for 12 hours. The polymer particulates were then collected byfiltration and dried for 24 hours.

Sample 2: Sample 1 was repeated except 0.05 g anionic surfactant (sodiumdodecylbenzenesulfonate-SDBS) was combined with the polymer particulatesand the 10,12-pentacosadiynoic acid in the ethanol.

Sample 3: Sample 1 was repeated except 0.05 g cationic surfactant(cetyltrimethylammonium bromide-CTAB) was combined with the polymerparticulates and the 10,12-pentacosadiynoic acid in the ethanol.

Sample 4: Sample 1 was repeated except 0.4 g hydrophobically modifiedsilica nanoparticles (AEROSIL R972, dimethyldichlorosilane modified,90-130 m²/g surface area by BET) were included in the silicone oilduring melt emulsification. Isolation of the polymer particulates andincorporation of the 10,12-pentacosadiynoic acid were conducted asabove.

Sample 5: Sample 1 was repeated except 0.4 g hydrophobically modifiedsilica nanoparticles (AEROSIL RX50, hexamethyldisilazene modified, 25-45m²/g surface area by BET) were included in the silicone oil during meltemulsification. Isolation of the polymer particulates and incorporationof the 10,12-pentacosadiynoic acid were conducted as above.

Sample 6: Sample 1 was repeated except 0.4 g hydrophobically modifiedsilica nanoparticles (AEROSIL R812S, hexamethyldisilazene modified,195-245 m²/g surface area by BET) were included in the silicone oilduring melt emulsification. Isolation of the polymer particulates andincorporation of the 10,12-pentacosadiynoic acid were conducted asabove.

Sample 7: Sample 1 was repeated except 0.4 g hydrophobically modifiedsilica nanoparticles (AEROSIL R812S, hexamethyldisilazene modified,195-245 m²/g surface area by BET) were included in the silicone oilduring melt emulsification, and 0.05 g anionic surfactant (sodiumdodecylbenzenesulfonate-SDBS) was combined with the polymer particulatesin ethanol along with the 10,12-pentacosadiynoic acid. Isolation of thepolymer particulates and incorporation of the 10,12-pentacosadiynoicacid were conducted as above.

Sample 8: Sample 1 was repeated except 0.4 g hydrophobically modifiedsilica nanoparticles (AEROSIL R812S, hexamethyldisilazene modified,195-245 m²/g surface area by BET) were included in the silicone oilduring melt emulsification, and 0.05 g cationic surfactant(cetyltrimethylammonium bromide-CTAB) was combined with the polymerparticulates in ethanol along with the 10,12-pentacosadiynoic acid.Isolation of the polymer particulates and incorporation of the10,12-pentacosadiynoic acid were conducted as above.

Sample 9: Sample 1 was repeated except 0.4 g hydrophilic fumed silicananoparticles (AEROSIL 380, 350-410 m²/g surface area by BET) wereincluded in the silicone oil during melt emulsification. Isolation ofthe polymer particulates and incorporation of the 10,12-pentacosadiynoicacid were conducted as above.

Sample 10: Sample 1 was repeated, except ethanol was substituted withheptane when incorporating the 10,12-pentacosadiynoic acid.

Sample 11: Sample 2 was repeated, except ethanol was substituted withheptane when incorporating the 10,12-pentacosadiynoic acid.

Sample 12: Sample 3 was repeated, except ethanol was substituted withheptane when incorporating the 10,12-pentacosadiynoic acid.

Sample 13: Sample 4 was repeated, except ethanol was substituted withheptane when incorporating the 10,12-pentacosadiynoic acid.

Sample 14: Sample 5 was repeated, except ethanol was substituted withheptane when incorporating the 10,12-pentacosadiynoic acid.

Sample 15: Sample 6 was repeated, except ethanol was substituted withheptane when incorporating the 10,12-pentacosadiynoic acid.

Sample 16: Sample 7 was repeated, except ethanol was substituted withheptane when incorporating the 10,12-pentacosadiynoic acid.

Sample 17: Sample 8 was repeated, except ethanol was substituted withheptane when incorporating the 10,12-pentacosadiynoic acid.

Sample 18: Sample 9 was repeated, except ethanol was substituted withheptane when incorporating the 10,12-pentacosadiynoic acid.

Table 1 below summarizes the composition of Samples 1-18 prepared asabove. The average particle size (D50) of Samples 1-9 was 82 microns andspan was 1.865. For Samples 10-18, the average particle size was 72microns and the span was 2.182. Average particle size measurements weredetermined by light scattering using a Malvern Mastersizer 3000 Aero Sparticle size analyzer. Glass bead control samples having a diameterwithin the range of 15 μm to 150 μm under the tradename Quality AuditStandards QAS4002™ obtained from Malvern Analytical Ltd. were used.Samples were analyzed as dry powders dispersed in air using the drypowder dispersion module of the Mastersizer 3000 Aero S. Particle sizeswere derived using the instrument software from a plot of volume densityas a function of size.

TABLE 1 Sample No. Silica Type Surfactant Solvent 1 none none ethanol 2none SDBS ethanol 3 none CTAB ethanol 4 AEROSIL R972 none ethanol 5AEROSIL RX50 none ethanol 6 AEROSIL R812S none ethanol 7 AEROSIL R812SSDBS ethanol 8 AEROSIL R812S CTAB ethanol 9 AEROSIL 380 none ethanol 10none none heptane 11 none SDBS heptane 12 none CTAB heptane 13 AEROSILR972 none heptane 14 AEROSIL RX50 none heptane 15 AEROSIL R812S noneheptane 16 AEROSIL R812S SDBS heptane 17 AEROSIL R812S CTAB heptane 18AEROSIL 380 none heptane

Samples obtained through ethanol incorporation of the10,12-pentacosadiynoic acid (Samples 1-9) experienced some swelling andaggregation, such that a free-flowing powder of polymer particulates wasnot obtained. In contrast, heptane incorporation of the10,12-pentacosadiynoic acid (Samples 10-18) afforded a free flowingpowder of polymer particulates.

Color Activation

Samples 1-18 were essentially white following their synthesis.Thereafter, a thin layer of sample deposited upon filter paper wasactivated through UV irradiation at 254 nm or sequential UV irradiationat 254 nm followed by heating at 50° C. or 150° C. UV irradiationquickly turned the samples blue (<10 seconds). Heating at 50° C. afterUV irradiation led to formation of a red to magenta color, whereasheating at 150° C. led to formation of a yellow color, as shown in FIGS.2A, 2B, 3A and 3B below. Both the red/magenta color and the yellow colorpersisted after heating was discontinued and the samples returned toroom temperature.

FIG. 2A shows photographs of Samples 1-9 after UV irradiation at 254 nm.FIG. 2B shows corresponding photographs of Samples 1-9 after UVirradiation and heat treatment at 50° C. As shown, a blue color resultedfrom UV irradiation (grayscale images in FIG. 2A, and left side ofsamples in FIG. 2B). Heating of a portion of the samples upon the filterpaper resulted in formation of a red to magenta color (grayscale imageson right side of samples in FIG. 2B). Coloration variation in the imagesresults from coverage irregularity arising from uneven drying of thesamples upon the filter paper.

FIG. 3A similarly shows photographs of Samples 10-18 after UVirradiation at 254 nm. FIG. 3B shows corresponding photographs ofSamples 10-18 after UV irradiation, followed by heat treatment at 50° C.or 150° C. As shown, a blue color again resulted from UV irradiation(grayscale images in FIG. 3A and right side of samples in FIG. 3B).Heating of a portion of the samples upon the filter paper at 50° C.resulted in formation of a red to magenta color (grayscale images onlower left side of samples in FIG. 3B). Further heating at 150° C. of aportion of the samples already heated at 50° C. resulted in formation ofa yellow color (grayscale images on upper left side of samples in FIG.3B). Neither color changed upon cooling the samples. Colorationvariation in the images results from coverage irregularity arising fromuneven drying of the samples upon the filter paper.

Among Samples 1-9, the lightest blue color was obtained in the absenceof silica nanoparticles and surfactants (Sample 1). Anionic and cationicsurfactants both increased the intensity of the blue color when nosilica was present (Samples 2 and 3). The blue color increased furtherin intensity when silica nanoparticles were present, and the strongestblue color was obtained in the presence of AEROSIL R812S silica (Sample6). In the presence of silica nanoparticles, anionic and cationicsurfactants had minimal effect on the intensity of the blue color.Colorspace measurements for Samples 1-9 obtained using an XRITE 528spectrophotodensiometer following UV irradiation for various times aresummarized in Table 2 below. L* (lightness), a* (green/yellow) and b*(blue/yellow) values were obtained for each irradiation time. Thecolorspace measurements were in general agreement with the qualitativevisual observations.

TABLE 2 Irradiation L* a* b* Time (s) 10 30 60 10 30 60 10 30 60 Sample1 67.95 67.44 68.03 −12.39 −12.26 −12.68 −23.42 −24.81 −24.05 Sample 245.74 40.86 41.63 −11.04 −10.35 −10.18 −31.22 −33.3 −32.17 Sample 334.45 35.24 23.27 −4.83 −4.66 −2.91 −33.18 −33.6 −33.13 Sample 4 55.1351.77 47.61 −11.78 −11.92 −9.95 −28.69 −28.62 −27.82 Sample 5 47.8545.06 45.58 −5.58 −5.3 −5.71 −30.31 −33.72 −33.03 Sample 6 30.36 24.7926.02 −5.95 −3.44 −4.28 −28.5 −28.07 −28.23 Sample 7 36.06 40.26 37.37−9.64 −9.76 −9.72 −28.46 −25.83 −27.8 Sample 8 36.39 37.67 35.69 −10.51−10.83 −10.25 −24.23 −24.09 −23.44 Sample 9 31.01 29.31 30.94 −2.79−1.63 −2.73 −32.28 −30.17 −32.11

FIG. 4A is a plot of colorspace lightness (L*) for Samples 1, 2 and 3 asa function of irradiation time. FIG. 4B is a plot of colorspacelightness (L*) for Samples 6, 7 and 8 as a function of irradiation time.FIGS. 5A and 5B are the corresponding plots of colorspace blue/yellowvalue (b*) as a function of irradiation time. As shown, consistentcolorspace lightness and colorspace blue/yellow values were reachedafter only a short irradiation time, and the values were only minimallyimpacted by the presence of anionic or cationic surfactants.

FIG. 6 is a plot of colorspace lightness (L*) for Samples 1, 4, 5, 6 and9 as a function of irradiation time. FIG. 7 is the corresponding plot ofcolorspace blue/yellow value (b*) as a function of irradiation time. Asshown, various grades of silica nanoparticles imparted different degreesof lightness to the polymer particulates, all of which were stronger incolor than in polymer particulates lacking silica nanoparticles. Theeffect of different types of silica nanoparticles on colorspaceblue/yellow values was considerably less pronounced. Minimal changes inthe colorspace lightness and colorspace blue/yellow values occurred atlonger irradiation times.

Among Samples 10-18, the lightest blue color was again obtained in theabsence of silica nanoparticles and surfactants (Sample 10). In general,samples containing silica nanoparticles (Samples 13-18) afforded adarker blue color. Colorspace measurements for Samples 10-18 obtainedusing a XRITE 528 spectrophotodensiometer following UV irradiation aresummarized in Table 3 below. L* (lightness), a* (green/yellow) and b*(blue/yellow) values were obtained for each irradiation time.

TABLE 3 Irradiation L* a* b* Time (s) 10 30 60 10 30 60 10 30 60 Sample10 69.04 54.73 49.19 −13.25 −14.15 −12.92 −15.46 −19.19 −20.26 Sample 1170.48 59.69 46.95 −11.26 −13.26 −12.58 −13.33 −15.09 −18.58 Sample 1264.70 52.97 42.85 −12.56 −13.97 −9.99 −17.20 −19.55 −18.70 Sample 1359.67 48.82 40.29 −12.50 −12.49 −9.43 −15.52 −19.63 −19.70 Sample 1462.60 48.86 41.70 −13.30 −12.28 −9.03 −17.73 −20.49 −18.44 Sample 1563.15 50.32 39.73 −13.59 −12.17 −8.47 −13.06 −16.96 −16.85 Sample 1660.18 46.22 40.81 −10.88 −11.19 −9.07 −13.19 −17.89 −18.20 Sample 1760.84 44.05 37.15 −13.14 −8.61 −3.80 −17.74 −19.92 −16.39 Sample 1860.97 46.89 45.60 −12.96 −12.40 −10.65 −14.88 −18.31 −16.39

The effect of thermal activation upon Samples 10-18 is shown in FIGS.8-10. FIG. 8 is a plot of colorspace lightness (L*) for Samples 10-18 asa function of heating temperature. As shown, initially blue samples(produced by UV irradiation) decreased somewhat in color brightness uponheating to 50° C. and 150° C. FIGS. 9 and 10 show plots of colorspacegreen/red value (a*) and colorspace blue/yellow value (b*),respectively, for Samples 10-18 as a function of heating temperature. Asshown the colorspace green/red value peaked at 50° C. and decreasedthereafter (FIG. 9), except for Samples 12, 14 and 18. The decrease incolorspace green/red values (a*) is consistent with the disappearance ofthe red to magenta color and formation of the yellow color upon furtherheating to 150° C. for all but Samples 12, 14 and 18. The limited changein a* for Samples 12, 14 and 18 is consistent with a lower degree ofvisible color change (FIG. 3B) for these samples upon heating to 150° C.Likewise, the colorspace blue/yellow values (b*) for all but Samples 12,14 and 18 increased upon heating from 50° C. to 150° C., againconsistent with ingrowth of the yellow color observed visually (FIG.3B).

All documents described herein are incorporated by reference herein forpurposes of all jurisdictions where such practice is allowed, includingany priority documents and/or testing procedures to the extent they arenot inconsistent with this text. As is apparent from the foregoinggeneral description and the specific embodiments, while forms of thedisclosure have been illustrated and described, various modificationscan be made without departing from the spirit and scope of thedisclosure. Accordingly, it is not intended that the disclosure belimited thereby. For example, the compositions described herein may befree of any component, or composition not expressly recited or disclosedherein. Any method may lack any step not recited or disclosed herein.Likewise, the term “comprising” is considered synonymous with the term“including.” Whenever a method, composition, element or group ofelements is preceded with the transitional phrase “comprising,” it isunderstood that we also contemplate the same composition or group ofelements with transitional phrases “consisting essentially of,”“consisting of,” “selected from the group of consisting of,” or “is”preceding the recitation of the composition, element, or elements andvice versa.

Unless otherwise indicated, all numbers expressing quantities ofingredients, properties such as molecular weight, reaction conditions,and so forth used in the present specification and associated claims areto be understood as being modified in all instances by the term “about.”Accordingly, unless indicated to the contrary, the numerical parametersset forth in the following specification and attached claims areapproximations that may vary depending upon the desired propertiessought to be obtained by the embodiments of the present invention. Atthe very least, and not as an attempt to limit the application of thedoctrine of equivalents to the scope of the claim, each numericalparameter should at least be construed in light of the number ofreported significant digits and by applying ordinary roundingtechniques.

Whenever a numerical range with a lower limit and an upper limit isdisclosed, any number and any included range falling within the range isspecifically disclosed. In particular, every range of values (of theform, “from about a to about b,” or, equivalently, “from approximately ato b,” or, equivalently, “from approximately a-b”) disclosed herein isto be understood to set forth every number and range encompassed withinthe broader range of values. Also, the terms in the claims have theirplain, ordinary meaning unless otherwise explicitly and clearly definedby the patentee. Moreover, the indefinite articles “a” or “an,” as usedin the claims, are defined herein to mean one or more than one of theelement that it introduces.

One or more illustrative embodiments are presented herein. Not allfeatures of a physical implementation are described or shown in thisapplication for the sake of clarity. It is understood that in thedevelopment of a physical embodiment of the present disclosure, numerousimplementation-specific decisions must be made to achieve thedeveloper's goals, such as compliance with system-related,business-related, government-related and other constraints, which varyby implementation and from time to time. While a developer's effortsmight be time-consuming, such efforts would be, nevertheless, a routineundertaking for one of ordinary skill in the art and having benefit ofthis disclosure.

Therefore, the present disclosure is well adapted to attain the ends andadvantages mentioned as well as those that are inherent therein. Theparticular embodiments disclosed above are illustrative only, as thepresent disclosure may be modified and practiced in different butequivalent manners apparent to one having ordinary skill in the art andhaving the benefit of the teachings herein. Furthermore, no limitationsare intended to the details of construction or design herein shown,other than as described in the claims below. It is therefore evidentthat the particular illustrative embodiments disclosed above may bealtered, combined, or modified and all such variations are consideredwithin the scope and spirit of the present disclosure. The embodimentsillustratively disclosed herein suitably may be practiced in the absenceof any element that is not specifically disclosed herein and/or anyoptional element disclosed herein.

1. A particulate composition comprising: a plurality of thermoplasticparticulates comprising a thermoplastic polymer, and a color-changingmaterial associated with the thermoplastic particulates, thecolor-changing material being both photochromic and thermochromic. 2.The particulate composition of claim 1, wherein the color-changingmaterial comprises one or more conjugated diynes.
 3. The particulatecomposition of claim 1, further comprising: a plurality of nanoparticlesdisposed upon an outer surface of each of the plurality of thermoplasticparticulates, the plurality of nanoparticles comprising a plurality ofoxide nanoparticles.
 4. The particulate composition of claim 3, whereinthe plurality of oxide nanoparticles comprises a plurality of silicananoparticles.
 5. The particulate composition of claim 1, furthercomprising: a surfactant associated with an outer surface of thethermoplastic particulates.
 6. A printed object comprising: a polymermatrix comprising a thermoplastic polymer; and a color-changing materialassociated with the polymer matrix, the color-changing material beingboth photochromic and thermochromic.
 7. The printed object of claim 6,wherein the color-changing material comprises one or more conjugateddiynes or a polymerized form thereof.
 8. The printed object of claim 7,wherein at least a majority of the one or more conjugated diynes ispresent as the polymerized form and the printed object has a firstcoloration state.
 9. The printed object of claim 8, wherein thepolymerized form is modified by heating and the printed object has asecond coloration state different from the first coloration state. 10.The printed object of claim 6, further comprising: a plurality ofnanoparticles present within the polymer matrix, the plurality ofnanoparticles comprising a plurality of oxide nanoparticles.
 11. Theprinted object of claim 10, wherein the plurality of oxide nanoparticlescomprises a plurality of silica nanoparticles.
 12. A method comprising:providing a particulate composition comprising a plurality ofthermoplastic particulates comprising a thermoplastic polymer, and acolor-changing material associated with the thermoplastic particulates,the color-changing material being both photochromic and thermochromic;and forming a printed object having a polymer matrix comprising thethermoplastic polymer and the color-changing material associated withthe polymer matrix.
 13. The method of claim 12, wherein forming theprinted object comprises: depositing the particulate composition in apowder bed; and consolidating a portion of the thermoplasticparticulates in the powder bed.
 14. The method of claim 12, furthercomprising: exposing at least a portion of the printed object to firstactivation conditions sufficient to convert the color-changing materialinto a polymerized form of the color-changing material having a firstcoloration state.
 15. The method of claim 14, wherein the firstactivation conditions comprise photoirradiation of the printed object.16. The method of claim 15, further comprising: exposing at least aportion of the printed object to second activation conditions sufficientto convert the polymerized form of the color-changing material into asecond coloration state different from the first coloration state. 17.The method of claim 16, wherein the second activation conditionscomprise thermal treatment of the printed object.
 18. The method ofclaim 12, wherein the color-changing material comprises one or moreconjugated diynes.
 19. The method of claim 12, wherein the plurality ofthermoplastic particulates further comprises a plurality ofnanoparticles disposed upon an outer surface of each of the plurality ofthermoplastic particulates, the plurality of nanoparticles comprising aplurality of oxide nanoparticles.
 20. The method of claim 19, whereinthe plurality of oxide nanoparticles comprises a plurality of silicananoparticles.